In many fields of technology, magnetic-field sensors are employed to detect movements of objects, for example. In some applications, a magnetic field acting upon the magnetic-field sensor is influenced by the movement of the respective objects such that conclusions may be drawn in terms of the movement of the object on the basis of the change in the magnetic field detected by the magnetic-field sensor.
Examples are found, among others, in the field of automobile applications, the movement of wheels being monitored in the context of an ABS application (ABS=antilock system), for example, using respective magnetic-field sensors. Other applications in the field of automobile technology include observing or monitoring the movement of crankshafts, camshafts and other shafts in the field of motor vehicles.
Depending on the specific implementation of respective magnetic-field sensors, they comprise so-called back-bias magnets which are located in a fixed arrangement with regard to the actual magnetic sensor elements of the magnetic-field sensor. In such a magnetic-field sensor, the magnetic field detected by the magnetic-field sensor itself may thus be at least partly caused by the back-bias magnet. The object whose movement is to be monitored, for example, via the magnetic-field sensor, possibly influences and/or supplements, by magnets or magnetic components of its own, the bulk magnetic field which will then be detected by the magnetic-field sensor.
Depending on the technology employed in the context of the actual magnetic-field sensor elements, the back-bias magnets, which are frequently implemented as permanent magnets, have different requirements. This may be accounted for, among other things, by the fact that some magnetic-field sensor element technologies are sensitive to different magnetic-field components, exhibit different responses to magnetic fields, and comprise different magnetic-field boundaries specific to the respective type.